Author: Katy Giombolini

Abstract: As dams are more frequently approaching relicensing by the United States Regulatory Commission, we are beginning to see the removal of dams along rivers and streams across the United States. The maintenance, relicensing, and upgrade costs are major determinants in dam decommissioning. The Marmot Dam located on the Sandy River in Oregon was removed beginning in July of 2007 because it was uneconomical for the Portland General Electric company to maintain the dam. It was one of the largest dams, in terms of height and sediment storage, in the Western United States. Its removal attracted the attention of the scientific community because little was known about the effects such a large amount of sediment flowing down the river would have on the basic river ecosystem and geomorphology. My research paper compares studies modeling what would happen on the Sandy River (regarding stream discharge, sediment transport, and sediment deposition) following dam breaching, to what actually occurred. The objective is to determine the extent in which we can rely on models to determine dam removal outcomes. This paper also discusses the need for tools that effectively address the future of dam removal policy in the United States.

Key References:
Doyle, M.; Stanley, E.; Harbor, J.; Grant, G. (2003). Dam removal in the United States: emerging needs for science and policy. Eos, 84, 29,32–33.

Major, J. J., J. E. O'Connor, G. E. Grant, K. R. Spicer, H. M. Bragg, A. Rhode, D. Q. Tanner, C. W. Anderson, and J. R. Wallick. (2008). Initial Fluvial Response to the Removal of Oregon's Marmot Dam. Eos Trans. AGU, 89, 27, 241-252.

Matthews, Graham and Smokey Pittman. (2008, September). Sand River Sediment Transport Monitoring Project. Graham Matthews and Associates WY2008 Annual Reportprepared for Portland General Electric.

Stillwater Sciences. (March 2000). Numerical Modeling of Sediment Transport in the Sandy River, OR Following Removal of Marmot Dam. Supplement to Environmental Assessment for the Bull Run Hydroelectric Project FERC Project no. 477prepared for Portland General Electric.

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